A large body of evidence has accumulated to substantiate the accuracy of functional MR measurements of both ventricles. Because of good accuracy and superior reproducibility, MR imaging may be considered the gold standard for in vivo quantification of left and right ventricular ejection fraction, myocardial mass, and wall stress. New prospects for functional MR imaging include determination of the end-systolic volume-pressure relation as an index of myocardial contractility. The ability of MR imaging to detect wall motion disturbances may be enhanced further by combining myocardial tagging techniques with finite element analysis. Conventional MR imaging is limited by long examination times, but recent ultrafast modifications of echo-planar imaging allow completion of a functional heart study within seconds. Implementation of ultrafast MR imaging will greatly increase the usefulness of MR imaging for routine evaluation of cardiac function.